Conventionally, resin components (molded bodies) have been often used as components of an image output apparatus utilizing an electrophotographic technique, a printing technique, or an inkjet technique such as a copier and a laser printer, and as inner components of an electric and electronic apparatus such as a home electric appliance and of a vehicle. These components have been demanded to have fire retardancy as a resin material that prevents the spread of fire.
In particular, a copier includes a fixing unit that generates a high temperature. A resin material is also used around the fixing unit. Further, a copier includes a unit that generates a high voltage such as a charging unit and an alternating current power source unit at 100 V used as a power source unit. The maximum power consumption of these high voltage units is about 100 to 1500 W, and they are formed of a unit that uses a power source system of 100 V and 15 A. Such a copier represented mainly by a multifunction printer is a stationary (floor-type) electric and electronic apparatus. According to an international standard (IEC60950) related to the fire retardancy of a resin material, which is a safety standard of product devices, a component which might be an ignition source or cause fire is required to be covered with an enclosure component having fire retardancy “5V” of a UL94 standard (Underwriters Laboratories Inc., standard). A test method related to the UL94 standard “5V” is defined as “a burn test by a 500 W test flame” by an international standard IEC60695-11-20 (ASTM D5048). As components which constitute a body of a copier, a component inside the enclosure as well as the enclosure component is required to satisfy “V-2” of the UL94 standard.
There are several kinds of fire retardants. Among them, a bromine system fire retardant, a phosphoric acid system fire retardant, a nitrogen compound system fire retardant, a silicone system fire retardant, and an inorganic system fire retardant are generally used. Fire retardant mechanisms of these fire retardants have already been disclosed in several documents. Here, three fire retardant mechanisms that are particularly used often are briefly described.
First is a halogen system compound represented by a bromine system fire retardant. A halogen system compound functions as an oxidation reaction negative catalyst with respect to a burning flame, and thereby burning speed is reduced.
Second is a phosphoric acid system fire retardant or a silicone system fire retardant. By causing the silicone system fire retardant to bleed on a surface of the resin while burning or causing a dehydration reaction of the phosphoric acid system fire retardant in the resin, carbide (carbonaceous residue) is generated on the surface of the resin. By forming a thermal barrier coating film and the like by using the carbide, the burning of the resin is stopped.
Third is an inorganic system fire retardant such as magnesium hydrate and aluminum hydrate. By an endothermal reaction caused when these compounds are dissolved by burning of the resin and an evaporative latent heat of generated water, the entire resin is cooled down; thereby the burning of the resin is stopped.
On the other hand, a conventional resin material has been formed of a plastic material using petroleum as a raw material. In recent years, a biomass-derived resin using plants and the like as a raw material has been attracting attention. A biomass resource is formed of a resource of organisms such as plants and animals, for example, wood, corn, soybeans, fat of animals, and raw garbage. The biomass-derived resin is formed by using these biomass resources as a raw material. In general, there has been a biodegradable resin. Biodegradation is a function of degradation caused by microbes under a certain environment such as a temperature, humidity, and the like. Some of the biodegradable resins are petroleum-derived resins having a biodegradation function. As the biomass-derived resins, there are polylactic acid (PLA) formed of a chemical polymer using, as a monomer, lactic acid formed by fermenting carbohydrate of potatoes, sugarcane, corn, and the like; esterification starch including starch as a major component, microbiologic production resin (Poly Hydroxy Alkanoate (PHA)) which is polyester in which microbes are produced inside; PTT (Poly Trimethylene Terephthalate) formed by using 1.3 propanediol obtained by a fermentation method and petroleum-derived terephtal acid as raw materials; and the like.
The petroleum-derived raw materials are used currently; however, research has advanced to transition from the petroleum-derived materials to the biomass-derived resins in the future. For example, succinic acid as one of major raw materials of PBS (Poly Butylene Succinate) has been manufactured by using a plant-derived material. Among such biomass-derived resins, a product formed by applying polylactic acid having a high melting point of about 180° C., superior moldability, and capable of being supplied at a stable rate to the market, has been realized. However, the polylactic acid has a low glass transition point of 56° C., and thus has low heat resistance with a heat deforming temperature of about 55° C. Since the polylactic acid is a crystalline resin, its shock resistance is low and Izod impact strength is 1 to 2 kJ/m2. Therefore, there has been a problem in that it is difficult to employ polylactic acid as a resistant member such as a component of an electric and electronic apparatus product. As a countermeasure for this problem, physical properties of the polylactic acid have been improved by forming a polymer alloy with a polycarbonate resin which is a petroleum-based resin, and the like. However, in this case, the rate (percent) of content of the petroleum-based resin has been increased while the rate of content of the biomass-derived resin has been decreased to about 50%. As a result, there has been a problem in that an effect against global warming for reducing the amount of fossil fuel to be used and the amount of carbon dioxide emission as a countermeasure for reducing the environmental impact is reduced to half.
For example, Patent Document 1 discloses a resin composition formed by blending 5 to 95 mass % of a polylactic acid resin (a), 5 to 95 mass % of an aromatic polycarbonate resin (b), and further, 0.1 to 50 parts by mass of a polymer compound (c) including an acrylic resin or a styrene resin unit which is grafted, and 0.1 to 50 parts by mass of a fire retardant (d) with respect to 100 parts by mass of a total of (a) and (b). In Patent Document 1, the fire retardant (d) is formed of one or more kinds selected from the bromine system fire retardant, phosphoric acid system fire retardant, nitrogen compound system fire retardant, silicone system fire retardant, and inorganic system fire retardant.
Although a biomass material is used as a countermeasure for global warming in Patent Document 1, its effect is reduced to half. Moreover, to obtain fire retardancy, 15 to 20 parts by mass of a phosphoric acid system fire retardant are required to be added with respect to 100 parts by mass of the resin. Since the phosphoric acid system fire retardant used here is formed by using a fossil resource, the rate of content of the used biomass material is further reduced.
Patent Document 2 discloses an electric and electronic component formed by molding a resin composition. The resin composition is formed by blending 1 to 350 parts by mass of a naturally-derived organic filler with respect to 100 parts by mass of a plant resource-derived resin. In this electric and electronic component, a polylactic resin is used as the plant resource-derived resin, and at least one kind selected from paper powder and wood powder is used as the naturally-derived organic filler, in which powder of waste paper is used as 50 mass % or more of the paper powder.
In Patent Document 2, the mechanical strength and the like of the resin are improved by adding the naturally-derived organic filler such as paper powder to polylactic acid. However, to obtain the fire retardancy, 23 to 29 parts by mass of a fire retardant formed by using a fossil resource such as a phosphoric acid system fire retardant are required to be added with respect to 100 parts by mass of polylactic acid. In this case, even when the resin material used as a base material is changed to a biomass material to reduce the environmental impact, the effect of reducing the environmental impact is reduced.
Patent Document 3 discloses a resin composition including at least one kind of organic polymer compound which exhibits biodegradability, a fire retardant-based additive including a phosphorated compound, and at least one kind of hydrolysis inhibitor which inhibits hydrolysis of the above-described organic polymer compound.
In Patent Document 3, however, to cause the organic polymer compound such as polylactic acid that exhibits biodegradability to be fire retardant, 30 to 60 parts by mass of the fire retardant-based additive including the phosphorated compound are required to be added with respect to 140 parts by mass of the organic polymer compound. Since the fire retardant-based additive including the phosphorated compound is formed by using a fossil resource as a raw material, the rate of content of the used biomass material is reduced.
In this manner, to cause a resin to be fire retardant, a large amount of fire retardant is required to be added. Normally, 10 to 30 parts by mass or as much as 50 parts by mass of fire retardant are required with respect to 100 parts by mass of the resin. When such a large amount of fire retardant is added to the resin, the rate of content of a used biomass material is reduced and the mechanical strength of the resin is reduced. When polylactic acid which originally has low impact strength is used, it becomes difficult to use the formed composition as it is as a consumer durable member.
As a technique to apply fire retardancy to a resin material formed by using a biomass material as a raw material, for example, Patent Document 4 discloses a manufacturing method of an organic-inorganic hybrid fire retardant cellulose material to solve the problem in that a conventional fire retardant material formed by using a petroleum material has a high impact on the environment. In the manufacturing method, acetyl cellulose (a) and 0.1 to 150 parts by mass of an alkoxysilane compound (b) with respect to 100 parts by mass of the acetyl cellulose (a) are blended to be evenly dispersed, an acetyl group is partially or completely detached, and the alkoxysilane compound is hydrolyzed and condensed.
However, the organic-inorganic hybrid fire retardant cellulose material obtained by this method includes acetyl cellulose and alkoxysilane compound simply kneaded together. According to a test result by a method pursuant to the UL94 burning test, the burning time of a test piece is extended but the test piece is completely burned out. Therefore, sufficient fire retardancy was not obtained. Moreover, as for moldability, although it is described that the formed resin can be molded, a specific embodiment regarding the moldability is not disclosed.
Further, in order to realize a fire retardant material which generates no toxic fumes such as dioxin, has fire retardancy, and is formed by using a biomass raw material, Patent Document 5 discloses a polymer composition including a polymer and a fire retardant which includes a polymer having a fire retardant compound as a side chain. Specifically, the fire retardant is formed by using a copolymer having a complex cyclic compound as a side chain, which complex cyclic compound has nitrogen as a heteroatom. As a part of a monomer of the polymer, a biogenic substance such as a nucleic acid base is used.
The fire retardant of Patent Document 5 has, as a side chain, the complex cyclic compound as a heteroatom in the polymer material. However, the polymer material as a base material is not a biomass material. Further, since the amount of additive is large, the environmental impact is not so small.
In such a conventional technique, a fire retardant is kneaded with a thermoplastic resin. By this method, the fire retardancy is realized; however, when the resin is to be used as a molded component through a molding process, there is a problem in that moldability is degraded and physical properties are reduced since fluidity of the resin is reduced due to a reduced affinity between the thermoplastic resin and fire retardant.
To solve the problem in that the dependency on a petroleum-based product is increased to obtain both fire retardancy and physical properties such as strength, Patent Document 6 discloses a fire retardant polyester resin composition. This fire retardant polyester resin composition is formed of 50 to 80 mass % of a naturally-derived biodegradable polyester resin (a) and 20 to 50 mass % of a thermoplastic polyester resin (b) in which an organic phosphorus compound is copolymerized. In specifics, polyethylene terephthalate (PET) or polybutylene succinate (PBS), in which an organic phosphorus compound is copolymerized, is blended with polylactic acid. However, polyethylene terephthalate (PET) of Patent Document 6 is formed of a petroleum-derived raw material, and succinic acid and butanediol serving as a raw material of polybutylene succinate are currently formed of a petroleum-derived raw material. Therefore, the composition disclosed in Patent Document 6 does not have much difference from a conventional fire retardant in respect of the rate of used biomass material. In this conventional technique, an organic phosphorus compound is copolymerized in a structure of the thermoploastic polyester resin, and the organic phosphorus compound is introduced in a main chain of the thermoploastic polyester resin. Due to the characteristics in realizing the fire retardancy by using the organic phosphorus compound, the fire retardancy is realized by detachment of phosphorus. However, since the organic phosphorus compound has been introduced in the main chain, it is not easily detached. Even when it is detached, the main chain of the thermoplastic polyester resin is broken. Thus, the amount of molecules is reduced and dripping is easily caused, which makes it difficult to obtain the fire retardancy. Consequently, even when a biomass-derived thermoplastic resin in which an organic phosphorus compound is copolymerized is used to realize the transition to less petroleum dependency, all of the physical properties and fire retardancy cannot be satisfied.
Non-patent Document 1 describes a case of chemically modifying phosphoric acid ester to be introduced in cellulose. However, there is only a description of a substance in which diethyl phosphoric acid ester is introduced in cellulose acetate. There is no description of a performance evaluation of the substance, in particular, an evaluation result related to fire retardant performance. Further, there is no description of kneading and polymerization with a thermoplastic resin.
Therefore, as a fire retardant resin composition which has low dependency on petroleum; includes a plant-derived material at a high rate; has a low environmental impact; and is provided with shock resistance, moldability, and fire retardancy, there has not been obtained a composition having a satisfactory performance yet, and further improvements and developments are required in the present circumstances.
[Patent Document 1] Japanese Patent Application Publication No. 2007-56247
[Patent Document 2] Japanese Patent Application Publication No. 2005-23260
[Patent Document 3] Japanese Patent Application Publication No. 2005-162872
[Patent Document 4] Japanese Patent Application Publication No. 2002-356579
[Patent Document 5] International Patent Publication No. 2003/082987
[Patent Document 6] Japanese Patent Application Publication No. 2004-256809
[Non-patent Document] C. S. Marvel et al., J. Polym. Sci., 6,351 (1951)